US 6877392 B2
In a gear, particularly for a robot, with a drive shaft and at least two parts rotatable relative thereto and to one another, in which a movement of one part is removable on its side remote from the other part, at least one of the rotary parts has a shaft connected in non-rotary manner thereto and which projects at least to the other part.
1. Gear for a robot having a drive shaft and first and second parts rotatable relative to the drive shaft and to one another, in which a movement of the first part is removable on a first end side remote from the second part, characterized in that at least one of the first parts part has a reference shaft connected in non-rotary manner thereto and which projects at least to the other part, said movement of said first part is additionally removable by means of said shaft on a second side facing said second part and remote from said first end side, an axis of said reference shaft is radially spaced from an axis of said drive shaft;
a bearing rotatably connects said first and second parts.
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The invention relates to a gear, particularly for a robot, having a drive shaft and at least two parts relative to the latter and to one another, in which a movement of one part is removable on its side remote from the other part, as well as a robot equipped with at least one such gear.
Multiaxial robots are e.g. known in the form of industrial robots and are used for the automatic performance of transportation and working processes. They generally have a carousel placed on a frame and rotatable about a primary axis and a structure mounted on the carousel and having a robot arm pivotable about several axes. For the mutual pivoting of the rotation axis of the robot, e.g. for rotating the carousel with respect to the stationary frame, gears are provided with a drive shaft and at least two parts rotatable relative to the latter and to one another, such as two half-shells or a gear shaft and a gearbox, on which is fixed in each case one of the robot parts pivotable about the particular robot axis. The movement of one part, e.g. the gearbox, must therefore be removable on its side remote from the other part, e.g. the gear shaft. The drive shaft is generally in operative connection with a drive motor.
In order to ensure a completely satisfactory and precise operation of the robot, sensor devices are required, which monitor and optionally limit the angular positions of the robot axes, so that an actual path of the angular position of the robot axes comparable with a desired path is obtained and the actual values can if necessary be adapted to the desired values.
It is often frequently desirable to subject an additional torque to at least one of the robot parts and this is scarcely possible with a conventional gear.
The problem of the invention is to further develop a gear of the aforementioned type in a simple and inexpensive manner in such a way that an arrangement of additional devices integrated into the gear, e.g. a sensor device or a device for subjecting one of the gear parts rotatable relative to one another with a torque, e.g. an auxiliary motor is possible.
According to the invention this problem is solved in the case of a gear of the aforementioned type in that at least one of the rotary parts has a shaft connected in non-rotary manner thereto and which extends at least up to the other part.
As a result of the construction according to the invention an additional shaft is provided connected in non-rotary manner with the rotary part of the gear and having an arrangement of additional devices, such as sensor devices, movement limiting devices, auxiliary motors, etc., integrated into the gear, e.g. arranged within the same or directly on the same, located on the side of one gear part facing the other part. Therefore the movement of the one rotary part of the gear equipped with the additional shaft both on its side remote from the other gear part rotatable relative thereto, such as is known in the case of conventional gears and also on its side facing the other part on the shaft projecting thereto, which in particular permits a determination of the relative movement of the two gear parts rotatable relative to one another.
Whereas the movement of the one gear part provided with the additional shaft projecting to the other gear part can fundamentally be removed on the side of the other part facing said part, according to a preferred development the shaft located on one part traverses the other part to its side remote from the first part. In this way the movement of the one part can be removed by means of the shaft traversing the other part on the side of the latter remote from the part with the shaft, which is particularly advantageous for space saving reasons in the case of a robot in order to bring about a high compactness of the gear or the complete arrangement of the robot joint.
According to a preferred construction the shaft located on the one part is the drive of a sensor device located in and/or on the other part and the sensor device can e.g. be constructed as a monitoring device for determining and/or limiting rotation parameters. As a result of the inventive gear construction in the case of such a sensor device integrated into the gear mechanical damage or dirtying of the sensor device is largely avoided and consequently it is possible to ensure a continuous determination and monitoring of the angular position of the rotation axis and optionally limit the rotation angle. The integration of the sensor device into the gear also leads to a more compact construction of the robot, excluding an undesired restriction to the mobility of the robot rotation axes as a result of the sensor device.
According to a preferred development the sensor device has a stub shaft guided in a receptacle and determines the rotation angle between stub shaft and receptacle. Such sensor devices are known per se. They are generally positioned substantially coaxially to the robot rotation axis and have e.g. on the face of the stub shaft located in the receptacle optical, magnetic or electromagnetic transducers, which determine and/or monitor the angular position of the particular rotation axis. On rotating the transducer or stub shaft with respect to the receptacle of the sensor device, the rotation angle is determined by a mechanism located in the receptacle, such as a diode in conjunction with a photoreceiver.
Whereas the sensor device receptacle is advantageously placed on one gear part, the sensor device stub shaft is preferably connected in non-rotary manner to the shaft located on the other gear part projecting up to or traversing the first gear part. If e.g. the one gear part is constructed in the manner of a gearbox and the other part in the manner of a gear shaft, then the sensor device receptacle can be positioned in the vicinity of the gear shaft face facing the gearbox and substantially coaxially to the robot rotation axis, whereas the stub shaft is located on the gear shaft projecting up to the gearbox. The receptacle can either be located on the inside facing the gear shaft or on the gearbox outside remote from the gear shaft, the stub shaft connected in non-rotary manner to the gear shaft in the latter case traversing the gearbox.
Alternatively e.g. the sensor device receptacle can be connected in non-rotary manner to the gear shaft, whilst the stub shaft is located on the gearbox shaft projecting up to and e.g. traversing the gear shaft. The monitoring device can therefore be positioned e.g. in the vicinity of the gear shaft face facing or also remote from the gearbox.
As has already been stated, in a preferred construction there is an optical, electrical, electromagnetic or magnetic monitoring device, particularly a resolver, which can e.g. be connected to a torque compensator for the particular rotation axis or to a control device for adapting the robot movement data.
According to another preferred construction the shaft located on one part can be subject to the action of a torque, which can e.g. be supplied by means of an auxiliary motor.
The drive shaft is preferably a high speed side driven shaft of a drive motor or is connectable thereto, so that the rotary parts of the gear can be moved at a lower speed than the drive shaft.
The shaft located on one rotary part of the gear and projecting to the other part is appropriately arranged coaxially to the rotation axis of at least one of the rotary parts of the gear and preferably both gear parts rotatable relative to one another are coaxially positioned.
The gear is preferably a high speed reducing spur, bevel, worm or epicyclic gear, e.g. a planetary gear. Preferably the gear is a harmonic drive gear. Harmonic drive gears comprise an outer race with internal teeth in which engage external teeth of a flexible tube. The tube diameter is somewhat smaller than the outer race width, so that tooth engagement only occurs when the tube is elliptically deformed by an oval or elliptical solid of revolution rotating in its interior. As there is a minor difference in the number of teeth of the tube (flexspline) and outer race, the in particular driven side tube rotates slowly when the in particular drive side solid of revolution rotates. Such gears have a very small clearance and achieve high reduction ratios. They were widely used in the past distributed in robots due to their high precision. They are now largely displaced by other gears as a result of their disadvantages (limited robustness, skipping of teeth in the case of high loading, limited reverse efficiency), so that nowadays their use is largely restricted to small robots and hand axes.
The drive motor can be central, eccentric or under a finite angle, particularly a right angle, to the rotation axis of at least one of the gear parts.
The invention also relates to a robot equipped with at least one gear of the aforementioned type.
The invention is described hereinafter relative to an embodiment and the attached drawings, wherein show:
Whereas in the case of the gear 1 shown in
Gear 1 in
The gear shaft 3 is mounted by means of antifliction bearings, e.g. ball bearings 5 in the gearbox 4. In order to remove the movement of the gearbox 4 with respect to the gear shaft 3 on the side 3 b of said shaft 3 remote from the gearbox 4, the latter has a shaft 15, which traverses the gear shaft 3 and is connected in non-rotary manner to the gearbox 4. For transmitting the torque of the in particular high speed side drive shaft 7 is provided a gearwheel 16 located thereon and which meshes with a gearwheel 17 mounted in rotary manner on the gearbox 4, which in turn is in engagement with a gearwheel 18 connected in non-rotary manner to the gear shaft 3. Planet wheel 18 further on meshes with an internal gear 19 formed on the interior wall of the gearbox 4. The gearwheels 16, 17, 18 make it possible to increase the torque of the drive motor 6 and bridge the eccentric arrangement of its drive shaft 7 with respect to the gear axis 2.
The gear 1 shown in
For determining and monitoring the rotation angle of the gear shaft 3 with respect to the gearbox 4 a sensor device 10 is positioned coaxially to the robot rotation axis 2. The sensor device 10 comprises a stub shaft 12 guided in a sensor casing or receptacle and which is connected in non-rotary manner by means of a coupling 11 to a shaft 15 of the gear shaft 3 projecting to the gearbox 4 and determines the rotation angle between stub shaft 12 and receptacle 13. The receptacle 13 of the sensor device 10 is located on the outside 4 b of the e.g. stationary gearbox 4 remote from the gear shaft 3 and the stub shaft 12 connected by means of the coupling 11 to the gear shaft 3 engages in the gearbox 4. The coupling 11 can e.g. be constructed as a compression or bellows coupling or the like. The drive motor 6 on gear shaft 3 is positioned centrally to the rotation axis 2 in the construction shown.
The sensor device 10 is e.g. constructed as a monitoring device for determining and/or monitoring the rotation angle between the gearbox 4 and gear shaft 3 and is connected e.g. to a torque compensator for the robot rotation axis 2 (not shown).
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Alternatively it is possible to provide on the gear shaft 3 a not shown shaft traversing the gearbox 4 to its side remote from the gear shaft 3 and on which can be located with respect to the gearbox 4 the sensor device.